This invention relates generally to improvements in synchronous or toothed belts through use of tougher tooth cover fabric designs, more particularly to use of fabrics with both high elongation and high strength in the belt longitudinal direction, and specifically to use of a fabric with a greater Fabric Tensile Toughness as defined herein.
Synchronous belts are those having teeth on at least one side designed for intermeshing with compatible grooved pulleys for positive engagement and synchronized motion or power transfer. These toothed belts generally have an elastomeric belt body with an embedded tensile cord of high tensile strength and modulus to maintain tooth pitch under tension. The tooth surface may be covered with a fabric or film to enhance wear resistance or to support the cord. Early toothed belts such as disclosed in U.S. Pat. No. 2,507,852 utilized duck, a firm, heavy plain-weave fabric. Duck and other fabrics of limited stretch required preforming of the tooth shape. Stretchable fabric was introduced in U.S. Pat. No. 3,078,206 to allow flow-through molding wherein the fabric was conformed to the tooth shape during molding as the rubber was forced through the cord line and into the mold grooves pushing the fabric ahead of it. Stretchable fabric based on high tensile-strength, crimped nylon was disclosed, for example, in U.S. Pat. No. 4,826,472. The crimping or texturing was by the false-twist method.
Special fabric adaptions were developed for particular belts as needed. U.S. Pat. No. 3,964,328 discloses fabric tooth cover with a polyethylene laminate which provides a low coefficient of friction and prevents low-viscosity, cast elastomers from penetrating to the belt surface. U.S. Pat. No. 5,362,281 discloses a fabric that was double woven with two sets of warp and weft yarns tied together in a single layer, which proved useful in 14-mm-pitch, round-toothed belts, the contents of which are hereby incorporated herein by reference.
U.S. Pat. No. 5,529,545 discloses stretch fabrics incorporating aramid fibers. Since aramid yarns are difficult to make stretchable by texturing, the stretchable yarns were formed from elastic yarns covered with aramid and nylon.
U.S. Pat. No. 8,932,165 discloses use of a relatively thicker fabric in a toothed belt for increased durability, the contents of which are hereby incorporated herein by reference.
EP 2,072,857 A2 discloses a fabric with ratio of weft mass to warp mass in the range from 3.00 to 5.17. It also discloses that at least 60% of the linear fraction of all the weft threads cover the warp threads and face the tooth-side outer side of the belt. This is reported to improve noise in toothed belts.
EP 2,570,529 A1 discloses a fabric which can be used on the working surface of ribbed belts. The fabric is woven from a thermoplastic polymer, texturized yarn and having a warp extension at 2 kg-force, 25 mm-width sample of 5-60% and a weft extension at 2 kg-force 25 mm-width sample of 40-250%. The fabric may have high bulk texturized warp and weft yarns, preferably with low modulus, with high extension/stretch and low permeability.
What is needed is improved fabric constructions to advance synchronous belt technology to higher performance levels.